nvdimm: convert nvdimm_mr into a pointer

This way we can easily check if the region has already been inititalized
without having to rely on the size of an uninitialized region being 0.

Free the region in nvdimm_finalize() and not in unrealize() as we will
allow to create the region before realization in following patches.
Reviewed-by: NDavid Gibson <david@gibson.dropbear.id.au>
Reviewed-by: NIgor Mammedov <imammedo@redhat.com>
Signed-off-by: NDavid Hildenbrand <david@redhat.com>
Message-Id: <20180619134141.29478-11-david@redhat.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

hw/mem/nvdimm.c

@@ -43,7 +43,7 @@ static void nvdimm_set_label_size(Object *obj, Visitor *v, const char *name,
     Error *local_err = NULL;
     uint64_t value;
 
-    if (memory_region_size(&nvdimm->nvdimm_mr)) {
+    if (nvdimm->nvdimm_mr) {
         error_setg(&local_err, "cannot change property value");
         goto out;
     }
@@ -71,11 +71,18 @@ static void nvdimm_init(Object *obj)
                         NULL, NULL);
 }
 
+static void nvdimm_finalize(Object *obj)
+{
+    NVDIMMDevice *nvdimm = NVDIMM(obj);
+
+    g_free(nvdimm->nvdimm_mr);
+}
+
 static MemoryRegion *nvdimm_get_memory_region(PCDIMMDevice *dimm, Error **errp)
 {
     NVDIMMDevice *nvdimm = NVDIMM(dimm);
 
-    return &nvdimm->nvdimm_mr;
+    return nvdimm->nvdimm_mr;
 }
 
 static void nvdimm_realize(PCDIMMDevice *dimm, Error **errp)
@@ -102,9 +109,10 @@ static void nvdimm_realize(PCDIMMDevice *dimm, Error **errp)
         return;
     }
 
-    memory_region_init_alias(&nvdimm->nvdimm_mr, OBJECT(dimm),
+    nvdimm->nvdimm_mr = g_new(MemoryRegion, 1);
+    memory_region_init_alias(nvdimm->nvdimm_mr, OBJECT(dimm),
                              "nvdimm-memory", mr, 0, pmem_size);
-    nvdimm->nvdimm_mr.align = align;
+    nvdimm->nvdimm_mr->align = align;
 }
 
 /*
@@ -167,6 +175,7 @@ static TypeInfo nvdimm_info = {
     .class_init    = nvdimm_class_init,
     .instance_size = sizeof(NVDIMMDevice),
     .instance_init = nvdimm_init,
+    .instance_finalize = nvdimm_finalize,
 };
 
 static void nvdimm_register_types(void)

include/hw/mem/nvdimm.h

@@ -74,7 +74,7 @@ struct NVDIMMDevice {
      * it's the PMEM region in NVDIMM device, which is presented to
      * guest via ACPI NFIT and _FIT method if NVDIMM hotplug is supported.
      */
-    MemoryRegion nvdimm_mr;
+    MemoryRegion *nvdimm_mr;
 
     /*
      * The 'on' value results in the unarmed flag set in ACPI NFIT,